IntelAcademic_IoT_07_C-Cpp_Yocto

Intel Do-It-Yourself Challenge
Compile C/C++ for Galileo
Nicolas Vailliet
www.Intel-Software-Academic-Program.com
[email protected]
Intel Software
2014-02-01
Why ?
C/C++ code ?
Why C/C++ code ?
Arduino sketches and node.js scripts are great,
well known methods to develop smart objects.
But what if you want to write C/C++ code ?
Maybe you like it, or want better performance
or need to use certain C/C++ libraries.
CPU intensive code on a Galileo ?
After all the Quark SoC has a lot of power to offer,
processing data from sensors, sound or webcam can be
done on the Galileo board itself.
Why use a remote server if you can do it locally ?
Native code ?
Processor compatibility
The core inside the Intel Quark System on Chip is ia32.
The assembly is nearly the same as a Pentium processor.
It means you could easily develop, compile and even
execute on any regular Linux system running on an Intel
machine. It’s simple.
Libraries compatibility
Yocto has a specific set of libraries and Quark is 32bit,
that’s why you need to install a build environment
compatible with Yocto and Quark on your workstation.
Compile on the Galileo
Compile on the Galileo itself
Add gcc to Yocto
You can add gcc and tools to the Galileo Yocto build and
compile for Galileo on the Galileo itself. It works !
Performance
As the Galileo is not as fast as a workstation,
it’s not convenient for large projects.
Using Yocto?
Compile your code faster on your computer and then, run it
on Galileo!
Generate the cross compile toolchain
Yocto output files
Rebuild Yocto vs build for Yocto
Yocto can be used in two different ways. After a short configuration
phase, you will choose between generating a Linux file system file or
the cross compile development environment (or toolchain).
Source code from
repositories or local
projects
Toolchain
Yocto
Linux image
And then, it will take up to 8 hours to compile output files, on a
notebook (depending on system configuration and network connection
speed).
On a Sandy bridge workstation, it lasts less than 2 hours.
Cross compilation
Generating a cross compiler
This course will cover how to generate the cross compile
toolchain. But what is a cross compiler?
//C program
int main(){
Return 0;}
Cross compilation
with Yocto-generated
toolchain
Execution
A cross compiler allows you to compile a code for Intel
Quark SoC, on your computer, and then to move it to the
Galileo board to execute it.
You’ll need
Board Support Package Sources Version 1.0.0 for Intel Quark
An archive with all tools you need, available on Galileo drivers website.
https://communities.intel.com/docs/DOC-22226
To boot the image, you must update Galileo’s firmware to 1.0.0 (see Intel Arduino IDE v1.0.0).
Uclibc or Eglibc
You can compile your Yocto image with uclibc (smallest C library, a few Ko only). To do so,
follow this procedure without editing any files.
This procedure will allow you to have eglibc instead, which enable the use of Java and other
sophisticated software.
Storage and internet bandwidth
Make sure you have 100Gb available on your hard drive.
We’ll also need a good internet connectivity.
CPU
If you would like to rebuild the full Yocto OS or generate the cross compile toolchain, it will take
up to 8 hours on a workstation.
You’ll need
Linux
We’ll use Ubuntu 12.04
Packages
“sudo apt-get install build-essential sed wget cvs
subversion git-core coreutils unzip texi2html texinfo
libsdl1.2-dev docbook-utils gawk python-pysqlite2 diffstat
help2man make gcc g++ desktop-file-utils chrpath libgl1mesa-dev libglu1-mesa-dev mercurial autoconf automake
groff libtool xterm p7zip-full bitbake”
Procedure to generate the toolchain
Procedure (1/5)
Uncompress
7z x Board_Support_Package_Sources*.7z
Rename your BSP folder with a shorter name
mv Board_Support_Package_*** BSP_Galileo
Unpack
tar -xvzf meta-clanton_*.tar.gz
Go to the new Yocto home folder
cd meta-clanton_...
Procedure (2/5)
Setting up Yocto receipe
By default, Yocto is ready to compile a tiny Linux image or
cross compile toolchain.
But, we want to compile, debug and use libraries.
Asking for a full configuration:
Edit the setup.sh file.
- Set BB_NUMBER_THREADS and PARALLEL_THREADS to
“number of cores your processor has multiply by 3”.
- Set DISTRO ?= “clanton-full”
(to enabling eglibc, see next slide)
Save the file.
Procedure (3/5)
Download, compile and set up Poky, a tool used by Yocto
./setup.sh
source poky/oe-init-build-env yocto_build
Disable uClibc
It will disable uClibc, and replace it by EGlibC, which have more
features and is commonly used under Linux.
Edit “../meta-clanton-distro/recipes-multimedia/v4l2apps/v4lutils_0.8.8.bbappend”
Comment these 3 lines:
#FILESEXTRAPATHS_prepend := "${THISDIR}/files:“
#SRC_URI += file://uclibc-enable.patch
#DEPENDS += "libiconv"
Procedure (4/5)
Edit the default config
These options are set up for generating the associated Linux image
later.
You can (un)comment features you do (not) want. The image size will
be 2GB.
Edit ../meta-clanton-distro/recipes-core/images/image-full.bb :
IMAGE_INSTALL = "packagegroup-core-boot
${ROOTFS_PKGMANAGE_BOOTSTRAP} ${CORE_IMAGE_EXTRA_INSTALL}
packagegroup-core-basic packagegroup-core-lsb kernel-dev“
IMAGE_FEATURES += "package-management tools-sdk dev-pkgs toolsdebug eclipse-debug tools-profile tools-testapps debug-tweaks’’
IMAGE_ROOTFS_SIZE = “2048000" (this is a minimum)
Procedure (5/5)
Launch the incredible machine
It will compile the cross compile toolchain.
This is the step that will take a while….
# bitbake image-full -c populate_sdk
Install the environment
To use the new environment, execute the script:
./tmp/deploy/sdk/clanton-tiny-***-1.4.2.sh
This script can install the toolchain on another system
Link your new headers and libs
source /opt/clanton-full/1.4.2/environment-******-linux
You’re now ready to compile a program.
Linking, compiling, running
C/C++ programs
Linking and compiling
${CC} and ${CXX} variables
To compile a C program, use CC, a environment variable
referring to gcc for Intel Quark architecture (C compiler).
${CC} myfile.c –o myfile
And use ${CXX} instead of ${CC} to use g++ for Intel Quark
architecture (C++ compiler).
Need a library?
If you want to use a library, just add :
`pkg-config LIBNAME --libs`
at the end of the C++ compile command.
Try it with opencv or libusb-1.0 (cf. other courses).
Run your program
SSH and SCP
You are compiling on your workstation, but you need to
execute on the Galileo board. Remember to send the binary
over the network, scp is very convenient and secure (it uses
SSH).
scp mybinary [email protected]:~
Execute
You can now connect over SSH and execute your binary.
ssh [email protected]
./mybinary
Tips
Reuse the cross compile toolchain
Once you have generated the cross compile toolchain, you will
only need to execute this command:
>source /opt/clanton-full/1.4.2/environment-******-linux
You have to run this command every time you open a new
terminal/shell.
Using gcc and g++ to compile a program for your computer is
not recommended (it should not link the program properly).
Keep your Board Support folder if you plan to generate other
output files with Yocto.
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